Variable impedance



Jan. 19, 1943. H. J. CRAYMER 2,308,863

VARIABLE IMPEDANCE Fil ed Jan. 27; 1940 VAN/4 INVENTOR. HF/VP Y Jflmf'CF14 V0715 Q BY #5 ATTORNEY.

Patented Jan. 19, 1943 UNITED VARIABLE IIVIPEDANCE Henry James Craymer,Chelmsford, England, assignor to Radio Corporation of America, acorporation of Delaware Application January 27, 1940, Serial N0. 315,887In Great Britain March 7, 1939 8 Claims.

This invention relates to variable impedance elements such as, forexample, variable inductances and resistances. As applied to variableinductances, the primary, though not the exclusive application of theinvention, is to the provision of improved variable in-ductance suitablefor use in a high frequency generator required to cover a Wide range offrequency and for similar purposes. As applied to variable resistances,the invention is of quite general application.

The simplest form of variable inductance at present commonly used in awide range high frequency generator consists of a coil and means fordisconnecting or short-circuiting conductor turns in said coil forvarying the inductance. This type of arrangement has the defect that asthe inductance decreases the current increases and the resultantincrease in heating imposes a serious limitation. Another arrangementwhich is sometimes used comprises a number of conductor turns associatedwith links or external switches whereby the separate conductor turns maybe connected in series or parallel or seriesparallel to vary theinductance. This type of arrangement, though avoiding the defect ofexcessive heating, above referred to, presents the defects (1) that ifexternal connection links are used it is a comparatively slow matter tochange inductances, while, if external switches are used,

this greatly increases complication, and (2) provision is made only forcombinations of complete conductor turns so that only a limited numberof inductance values is obtainable and the inductance is notcontinuously variable.

The present invention as applied to inductances, seeks to avoid theabove defects.

According to this invention, a variable inductance or resistance devicecomprises a plurality of open rings which result in electricalinterrupted conductor turns positioned adjacent one another, each ringcarrying contact means located at the open point whereby it makeselectrical connection with its neighbor or neighbors, said ring orconductor turns being individually movably mounted with respect to oneanother, and the whole arrangement being such that by adjusting therelative positions of the rings the points at which they contact withone another may be varied and the inductance or resistance (as the casemay be) of the whole device thereby continuously varied from a conditionin which the resultant conductor turns are effectively in series to acondition in which turns are effectively in parallel.

The invention is illustrated in the accompanying drawing. Forconvenience of reference, the figures are numbered 1a, 1b, 1c, 2, 3a and3b. Figures la, 1b, 1c illustrate in simplified form one embodiment inthree positions of adjustment, while Figure 2 shows a modification, andFigures 3a and 3b illustrate a further modification.

Referring to Figures 1a, lb, 10, the coil therein illustrated comprisestWo open-ended rings-any number of rings might be used but only two areshown for the sake of simplicity-A and B being terminals of one ring,and C and D the terminals of the other. At A is a projecting contactmember X which makes sliding contact on the adacent ring near C, whileon the said adjacent ring at D is a similar contact device Y. whichcontacts with the first ring near B. The rings are coaxially mounted andindividually rotatable with respect to one another about the commonaxis. One terminal of the whole coil is at B, while the other terminalis at C, connection to C being made by means of a further contact deviceZ which slides on a fixed plate (not shown). Obviously, both rings neednot be rotatable for relative movement is all that is required; thus,the ring A, B, may be fixed and the turn C, D, rotatable. In Fig. 1a thetwo rings are connected together in parallel; in Figure 10 they are inseries. Fig. 1b shows one of the infinite number of intermediateadjustments obtainable between these two extreme values.

In view of the description already given, Fig. will be found largelyself-explanatory, this figure showing a three-conductor arrangementconsisting of interrupted rings AB, CD, and EF. Obviously, in Fig. 2 oneof the rings, preferably the intermediate ring CD may be fixed and theother two individually rotatable.

The contact devices illustrated are given only by way of example; forexample, the rings, themselves, may be arranged to be brought intocontact over portions that are in parallel in which case no projectingcontact devices will be necessary. Furthermore, the turns may be in theform of flat interrupted annuli spaced apart by discs of insulatingmaterial, the whole being mounted on a common axial member of insulatingmaterial. This makes a very strong compact structure. Again, by makingthe turns of required resistance material any of the embodimentsdescribed may be utilized as Variable resistances.

In some cases where only occasional adjustment is required, the slidingcontacts can be replaced by clamps, still retaining the same principles.Such a case is shown in Figs. 3a, 3b, wherein 3a is a section and 311 anend view. Two coil assemblies are shown linked together by a link L andturns of one of the assembli s are shown connected by clamps V.

Obviously, variable inductance or resistance devices in accordance withthis invention may be incorporated with known switch or link typevariable inductances or resistances-for example, in cases in which it isrequired to obtain a series of steps of inductance or resistance withcontinuous variation between the steps.

What is claimed is:

l. A variable impedance device comprising a plurality of fixed andmovable open rings of conductive material, said fixed and movable ringsalternately positioned coaxially in a row with a space between eachfixed and movable ring, a contact member secured to each ring andcontacting an adjacent ring and so located in the space between a fixedand movable ring that a sliclin contact is made to an adjacent ring whena movable ring is rotated with respect to a ixed ring.

2. A variable impedance device comprising a plurality of fixed andmovable open rings of conductive material positioned coaxially andalternately in a row with a space between each fixed and movable ring, awedge-shaped contact member located in said space and secured to one endof each ring, said wedge-shaped contact member having its pointed endprojecting in a direction toward an adjacent ring, said movable ringsarranged to contact and rotate relative to said fixed rings so that thepointed end of said contact member makes sliding contact with anadjacent ring to vary said impedance device.

3. A variable impedance device comprising a plurality of fixed andmovable open rings of conductive material, said fixed and movable ringsalternately positioned in a row with a space between each fixed andmovable ring, each ring being of the same diameter and coaxially mountedwith respect to an adjacent ring, a contact member carried by each ringand located within the space between a fixed and movable ring near theopen ends thereof for making a variable sliding contact with an adjacentring and for electrically connecting said rings together in parallel,Whereby the impedance of said device is continuously Varied.

4. A variable impedance device comprising a plurality of fixed andmovable open rings of conductive material, said fixed and movable ringsalternately positioned in a row with a space between each fixed andmovable ring, each ring being of Iii) the same diameter and coaxiallymounted with respect to an adjacent ring, a contact member carried byeach ring and located within the space between a fixed and movable ringnear the open ends thereof for making a variable sliding contact with anadjacent ring and for electrically connecting said rings together inseries, whereby the impedance of said device is continuously varied.

5. A variable inductance device comprising a plurality of fixed andmovable open rings of conductive material, said fixed and movable ringsalternately positioned in a row with a space between each fixed andmovable ring, each ring being of the same diameter and coaxially mountedwith respect to an adjacent ring, a contact member carried by each ringand located within the space between a fixed and movable ring near theopen ends thereof for making a variable sliding contact with an adjacentring and for electrically connecting said rings together in parallel,whereby the inductance of said device is continuously varied.

6. A variable impedance device comprising a plurality of open rings ofconductive material having internal electrical reactance, some of saidrings being fixed and some movable with respect to each other andalternately positioned with a space between, contact means positionedwithin said space and secured to each on of said rings, said contactmeans arranged to make electrical connection to an adjacent ring, saidmovable rings being individually mounted about a common axis withrespect to an adjacent fixed ring so that the movable rings make asliding contact with said fixed rings to continuously vary the impedanceof said device.

'7. A device as claimed in claim 6 wherein the rings of conductivematerial are mounted coaxially and are of the same diameter, saidmovable rings being adapted to be rotated about the common axis withrespect to an adjacent fixed ring, said contact means being adapted tomake a sliding contact with at least one adjacent ring.

8. A variable impedance device comprising two groups of coils, eachgroup including a plurality of fixed and movable open rings ofconductive material, said fixed and movable rings alternately positionedin a row about a common axis with a space between each fixed and movablering, a clamp member arranged to bridge over said space to contact twoadjacent rings and means to vary said device by changing the position ofsome of said movable rings with respect to said fixed rings. 1

HENRY JAMES CRAYMER.

